LIFE SCIENCE. Supplemental Curriculum. Science Activities in English and Spanish

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1 LIFE SCIENCE Supplemental Curriculum Science Activities in English and Spanish Produced by The New Mexico Museum of Natural History & Science as part of its Proyecto Futuro Initiative Printed in 2002

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3 TABLE OF CONTENTS Acknowledgments... i Introduction General Layout... 1 Activity Components... 1 Teaching Tips Cooperative Learning... 4 Teaching Outdoors... 5 Students with Special Needs... 5 Teacher Background Information Scientific Inquiry: Observation and the Scientific Method... 7 Record Keeping and Journals... 9 Introduction to Life Science Background Information Questions, Observations, and Hypotheses What Is a Living Thing? Using a Microscope Cell Dance Life Cycles Classifying Introduction to Fungi Background Information Growing Bread Mold Fungus A Fungus Is Not a Plant A Fungus Amongus Budding in a Bottle Rising Bread A Fungi Forest

4 Introduction to Plants Background Information What s Inside a Seed? Seed Dispersal Walk What Do Seeds Need to Germinate? What Comes out of a Leaf? The Living Leaf Smart Roots and Shoots Flowers, Fruits, and Cones A Diversity of Leaves Introduction to Animals: Invertebrates Background Information Symmetry Soil Invertebrates Earthworms Earthworm Work Isopod Feeding Habits Camouflage The Sponge: An Unusual Invertebrate Introduction to Animals: Vertebrates Background Information The Six Vertebrate Groups Egg Lab Bird Beak Banquet Bone Density Swim Bladder Thin Skin Lizard Adaptations Vertebrate Charades

5 Introduction to the Human Body Background Information The Human Machine Fingerprints Skeleton Sketch Muscles Voluntary and Involuntary Working Muscles Protein Digestion Heart Rate and Drugs Introduction to Ecology Background Information Food Chain Mobile The Water Cycle Ecosystem Scavenger Hunt Small Ecosystems on Campus Succession in Pond Water Biodiversity It s a Small World Appendix: Standards Alignment

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7 ACKNOWLEDGMENTS This curriculum supplement represents a collaborative effort led by the New Mexico Museum of Natural History & Science that includes educators, scientists, and other professionals to provide teachers of English and Spanish-speaking students in grades K- 8 with hands-on, auxiliary life science activities. The contents of this manual can be used as a framework to integrate inquiry-based activities into science teaching. This guide is part of the Museum s Proyecto Futuro Albuquerque (Project Future) initiative, a multi-year collaboration between the New Mexico Museum of Natural History & Science and participating principals, teachers, parents, and students from the Albuquerque Public Schools. The New Mexico Museum of Natural History & Science has implemented Proyecto Futuro with the purpose of improving science and mathematics teaching and learning for elementary and middle school grades by incorporating teacher professional development, bilingual curriculum materials, and family science workshops. This material is based upon work supported by the National Science Foundation under Grant No Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF). In addition to those listed below, we would also like to thank the following individuals for their editorial assistance with specific areas of the curriculum: Dave Hafner, Ph.D., Helen Haskell, Tish Morris, Mike Sanchez, Dolores Varela-Phillips, and Cary Weiner. Thanks also go to Mary Jo Daniel for aligning the activities in this curriculum to national, state, and local science and math Standards. Writing & Compiling: Layout & Design: Reviewing & Editing: Translation: Illustrations: Project Funding: Terry Dunn and Heidi L. Anderson Matt Celeskey, Roxanne Witt, Madeleine Zeigler Selena Connealy, Roxanne Witt, Madeleine Zeigler Marina Arbetman Rabinowitz, Ph.D. Terry Dunn and Chris Peknik General Mills Foundation, Minneapolis, MN National Science Foundation, Washington, D.C.

8 INTRODUCTION This supplemental life science curriculum is designed to be used in conjunction with other current science curricula and is intended to introduce K-8 students to biological concepts as well as encourage an interest in science in general. The activities in this manual were developed following local, state, and national science standards and benchmarks. Activities may be used to add inquiry-based and problem-solving approaches to the K-8 classroom; they are intended to give students hands-on experience with life science concepts while enhancing critical thinking skills. General Layout This supplemental curriculum begins with a general overview of life science. Subsequent sections of the curriculum are arranged in the hierarchical order of organisms used by taxonomists, beginning with fungi and continuing through invertebrates and vertebrates. The curriculum concludes with sections on the human body and ecology. The design of the curriculum includes a blend of elementary and middle school-level activities, indoor and outdoor activities, and activities that can be done individually, in small groups, or as a class. In many cases, there are suggestions for modifying the activities to different grade levels and to different classroom situations. Activity Components Considerable information is provided for the teacher within each activity. Please note that information that is provided primarily for the teacher s use is printed in English only. Information that the teacher may be distributing to students as well as key content and vocabulary is provided in both English and Spanish. Each section begins with background information, providing an overview of the content material for that section. Each of the activities contained in this supplemental curriculum contains the following components: Purpose The purpose is an overall description of the activity. Materials The materials section lists the materials needed to complete the activity. Concepts (Also provided in Spanish.) The concepts for each activity outline the principles students should learn while doing the activity. New Mexico Museum of Natural History & Science Proyecto Futuro 1

9 Introduction Grades (Provided in the box at the top of each activity.) The grades are a suggestion for what grade levels the activity may be appropriate for. With modifications, many activities can be used with older or younger students. Group size (Provided in the box at the top of each activity.) The group size is a suggestion for how to break up the class into groups for carrying out this activity and may be adjusted to fit the needs of the class and the teacher. Time (Provided in the box at the top of each activity.) Each activity includes an estimate of the time it will take to complete the activity. Some of the separate components of the activities can be completed over several days or weeks. Safety When there are safety issues, they will be listed in this section. Vocabulary (Also provided in Spanish.) Key words are listed in this section and highlighted throughout the text of the activity. In Advance This section describes the preparations you will need to make before introducing the activity. Procedure The procedure section is a step-by-step guide to presenting and conducting the activity. Questions to Ask During the Activity (Also provided in Spanish.) This section contains several questions to guide students actions and thinking processes while doing the activity. Why It Happens/More on the Topic (Also provided in Spanish.) In this section you will find explanations of what is occurring during the activity. This section also might contain additional background information pertaining to the activity. Modifications The modifications section contains suggestions for how to change the activity for different grade levels or for different situations. 2 New Mexico Museum of Natural History & Science Proyecto Futuro

10 Introduction Extensions The extensions section contains ideas for further investigation of the activity s topic. References The references are the sources of information used in the activity or additional resources that can be used by the teacher. New Mexico Museum of Natural History & Science Proyecto Futuro 3

11 Introduction TEACHING TIPS The Proyecto Futuro Life Science Curriculum is designed to provide educators with an assortment of flexible and stimulating activities. To maximize the effectiveness of the curriculum, review the following tips for integrating cooperative learning techniques, incorporating outdoor learning experiences, and working with all types of students. Cooperative Learning Many of the activities in the curriculum rely on cooperative learning principles. It has been shown that students can benefit from working in groups in several ways. Cooperative learning boasts academic achievement, helps students learn how to work together effectively, and increases the self-respect and self-direction of individual students. These improvements are particularly noticeable in students with limited English skills and in low achievers. The following tips will help you make the most of the cooperative learning strategy. 1. When assigning teams, be sure to include a diversity of learners. Consider achievement levels, language skills, learning styles, gender, and ethnicity. 2. Tell students that they should first try to solve problems and ask questions within their group before seeking help from the teacher. 3. Encourage students to work with their group, but also let them know that they are responsible for their own work. 4. Sometimes it will work best to assign roles within each group. Examples of roles include: the materials monitor to gather materials for the activity, a recorder to keep track of data and ideas, a reporter to report the group s findings to the class, a reader to read activity directions, and a time keeper to help the team complete tasks on time. 5. Establish and use a signal to gain attention of the class when necessary. 6. Monitor the groups throughout the activity to make sure they are on task and to assist with questions or problems. Your role should be as facilitator or consultant rather than instructor. 4 New Mexico Museum of Natural History & Science Proyecto Futuro

12 Introduction Teaching Outdoors Teaching and working outdoors presents some different challenges from working indoors. The boundaries are not as clear, there are many background noises, and there are potential hazards. Here are some tips for making your outdoor excursion a safe and positive learning experience. 1. Discuss with students the importance of respecting plants and animals outdoors. Students should not touch unfamiliar plants or animals they can be harmful. When observing or collecting plants and animals, students should disturb the area as little as possible. Rare plants or animals should not be collected. 2. Explain the activity and rules for working outside as much as possible before leaving the classroom. It will be harder for students to hear and to focus once you are outside. 3. Be sure to bring all the supplies you will need. It will not be easy to return to the classroom during the activity. 4. Once you are outside, identify the boundaries where students will be working. For instance, you may not want students to be out of view or playing on the playground equipment. Also consider directing students to areas where they will have the most success completing the activity. 5. Have a signal that can be used to get the attention of your students. Using a whistle, clapping your hands, or raising your arm are some possibilities. Students with Special Needs The activities in this curriculum can be modified to work with a variety of students. Here are some suggestions: 1. Try grouping a bilingual student with a student who has limited English proficiency. Write key words on the chalkboard sometimes the words from different languages look similar when written. Use pictures, diagrams, and demonstrations to explain instructions when possible. 2. Students with visual impairments may be given oral instructions or a copy of the activity with enlarged print. New Mexico Museum of Natural History & Science Proyecto Futuro 5

13 Introduction 3. Students with mobility impairments may be paired with a non-disabled partner when necessary. 4. With gifted students, allow extra time for questions and further investigation. 6 New Mexico Museum of Natural History & Science Proyecto Futuro

14 Introduction TEACHER BACKGROUND INFORMATION Scientific Inquiry: Observation and the Scientific Method In many ways, your students are probably already experts at noticing things that adults pass by. But, while many kids will notice obvious characteristics of objects, observing in the life sciences will require them to hone their observation skills. All five senses will be needed: sight, hearing, taste, touch, and smell. And once their observations are made, they will need to analyze and describe them in greater detail. Observation is one of the most important scientific skills and the first step in the scientific method. The scientific method is a set of steps used to systematically test ideas and find answers to questions. The steps of the scientific method include: 1) making an observation 2) formulating a hypothesis 3) designing and conducting an experiment to test the hypothesis 4) recording the results often with a table or graph 5) forming a conclusion [A simplified version of the steps in the scientific method for younger students is: Guess, Test, and Tell. Beginning with a problem, students propose a guess. Then they proceed to design a test for proving whether their guess is correct or not. After they have tested their guess, they tell the class their results.] In some cases, an observation is made by chance. Other times, a scientist seeks more information by doing library research or by talking with others. Regardless of how the observations are made, a question eventually forms and the scientist can begin taking steps to find an answer. Examples of some biological questions are: At what temperature do lizards become inactive? How fast do hummingbirds fly? What type of seed does a house finch like? The next step is to form a hypothesis based on the original observations. A hypothesis is a statement of a best guess answer to a question, or a prediction. It is important that the hypothesis is measurable. For example, after observing the feeder in your back yard, you might hypothesize that house finches like sunflower seeds. While we can t ask a finch which kind of seed it likes best, we can count the number and kind of seeds finches choose to eat at a feeder. So, a more testable hypothesis would be house finches eat mostly sunflower seeds. New Mexico Museum of Natural History & Science Proyecto Futuro 7

15 Introduction Next, the hypothesis is tested with an experiment. The easiest hypothesis to test is one with a yes or no answer or result. For example, you could give house finches sunflower seeds and another kind of seed, and then count how many of each kind the finches eat. The results of an experiment should either support or falsify the hypothesis. For example, if 80% of the seeds the house finches ate were sunflower seeds, the hypothesis would be supported in this case. The experiment might not always provide an answer to the hypothesis, though. Sometimes new questions arise. Frequently one trial of the experiment is not enough. What if you conducted your experiment by observing only one house finch on one day? Would you be able to conclude that house finches eat mostly sunflower seeds? Probably not. But if you were to observe 20 house finches, you might be able to predict that other groups of house finches under the same conditions would also eat mostly sunflower seeds. Each time you conduct your experiment under the same conditions, it is referred to as a replicate. When designing an experiment, it is also important to have a control. A control is the measuring stick that can be used as a comparison for experiment results. The control for the house finch study is a seed other than the sunflower seeds. If the only choice the house finch had was sunflower seeds (no control) it would be impossible to know whether house finches prefer sunflower seeds or just ate them when nothing else was available. The experimental variable is the portion of the experiment that is used to test the hypothesis. It is important that there be only one difference between the variable and the control. If there is more than one variable, it s difficult to tell which variable caused the results. For example, if you provided the finches with three different kinds of seeds small sunflower seeds, large sunflower seeds, and large thistle seeds and they chose the small sunflower seeds, it would not be clear whether the size of the seed was more important than the kind of seed. It is important to make sure that all the conditions between the control and variable are equal except the one attribute being tested. One of the most important features of a scientific experiment is that results can be duplicated each time the experiment is conducted. This helps ensure that the results are not just one-time, chance events. For instance, in the house finch experiment, it would be important to conduct the experiment under the same weather conditions, at 8 New Mexico Museum of Natural History & Science Proyecto Futuro

16 Introduction the same time of year, in the same type of habitat, using the same type of feeders. The results of the experiment should be similar with each trial before a final conclusion can be made. Finally, it is tempting to conclude that a hypothesis is proven true when the experiment results confirm the hypothesis. In science, however, results either support or falsify the hypothesis rather than prove it. It is always assumed that future experiments could change our ideas about what is true and what is false. For example, the same house finch experiment could be conducted during a different season of the year and we could find that house finches only prefer sunflower seeds in the summer, but not in the winter. This new data would only partially support the original hypothesis. Often students are disappointed when their hypothesis is not supported by experiment results. But there are no wrong or right answers when an experiment is designed and conducted well. Some of the most important discoveries occur when an experiment generates more questions rather than supporting the original hypothesis. In fact, some of the most interesting scientific breakthroughs have been purely accidental! Emphasizing this point with students will give them the freedom to think more creatively, to ask questions, and to experiment without fear of failure. Record Keeping and Journals Scientists often keep records of their observations. Sometimes the records are in the form of numbers in a table, drawings in the margins of a page, or written thoughts about their research topic. Record keeping in all of its forms allows a scientist to discover patterns and make connections between separate observations. Keeping a science journal can do the same for your students. Journal writing during and after activities will help sharpen their writing, reading, and communication skills, and will help them discover patterns and connections as they work their way through the activities. Many of the activities in this curriculum provide a Student Activity Sheet for students to record their observations and data. Encourage your students to keep an ongoing journal where they can enter their thoughts on the activities they are doing in the classroom and how they apply to their real world experiences. New Mexico Museum of Natural History & Science Proyecto Futuro 9

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18 Introduction to LIFE SCIENCE New Mexico Museum of Natural History & Science Proyecto Futuro 11

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20 Introduction Life Science BACKGROUND INFORMATION LIFE SCIENCE Characteristics of Living Things Living things (biotic) have a number of characteristics that make them different from non-living (abiotic) things. They are made of one or more cells. Living things have structures that perform specific functions. Living things maintain an internal environment. The internal environment can be that of a single cell or that of an entire multi-cellular organism. Living things require and use energy. The energy is used to carry out life functions. Life functions of living things can include respiration, excretion, movement, and growth. Living things reproduce, passing along genetic information to future generations. Living things change over time, or evolve. If an object does not have all these characteristics, it is not living. For example, light bulbs use energy and have an organized structure, but they do not move, respire, or reproduce. A marine sponge does not appear to move, but it does move during its early development and only later attaches itself to the sea floor or some other stationary object. While all living things have these characteristics in common, there are seemingly infinite variations on the theme. These variations give us the enormous diversity of life on Earth today perhaps between 10 and 100 million different species. To date, only about 1.4 million of these species have been identified. The Cell A cell is the smallest structural unit of life that is capable of functioning independently. In fact, cells are so small you could fit 9,000 of them, side by side, between the millimeter dashes on a ruler! Naturalists Robert Hooke and Anton van Leeuwenhoek were the first to view the microscopic world in the mid-1600s. It was Hooke who coined the term cell to describe the room-like partitions that he observed in cork through his microscope. New Mexico Museum of Natural History & Science Proyecto Futuro 13

21 Introduction Life Science Vacuole Golgi Body Mitochondria Cytoplasm Smooth Endoplasmic Reticulum Nucleus Rough Endoplasmic Reticulum Ribosome (attached to Endoplasmic Reticulum) Cell Membrane Lysosome All living things are made up of one or more cells, but not all cells are the same. For example, protist cells are very different from human nerve cells, which are very different from blood cells. However, there are some basic similarities among all cells. These characteristics allow cells to carry out their basic functions of 1) interacting with their environment, 2) harnessing energy, and 3) digesting and storing food. The cell membrane surrounds the outside of the cell. It is a thin layer made up of chemical compounds that act as a guard and gate to the inside of the cell. The cell membrane is semi-permeable, allowing only certain chemicals to enter or leave the cell. The inside of the cell contains cytoplasm. Cytoplasm is a viscous fluid that acts as the cell s blood by transporting food and other chemicals from one part of the cell to the other. Other parts of the cell are also anchored to the cytoplasm. The nucleus and the mitochondria are two of the structures that can be found in the cytoplasm. The nucleus houses the genetic instructions (genes made up of DNA) for the cell. These genetic instructions determine the type of cell (nerve, blood, or protist) and how it will function. The mitochondria are the power plants for the cell, where food is turned into energy that the cell can use. Lysosomes are another structure found in the cytoplasm. Lysosomes contain the enzymes used to break down food and discard waste products produced by chemical reactions in the cell. When the food is digested, the products are passed to the vacuoles. Vacuoles are also important in regulating water balance within the cell. For example, in plants, vacuoles help keep the plant stiff and rigid. When the vacuoles lose too much water, the plant wilts. 14 New Mexico Museum of Natural History & Science Proyecto Futuro

22 Introduction Life Science Change and Adaptation Organization and order is one characteristic of living organisms, but change is the rule. Change occurs at several different biological levels. It occurs at the level of the individual organism, within groups of organisms, and within ecosystems. For instance, an individual organism changes as it grows and matures. A newborn wolf is different in shape, size, and behavior from that of an adult wolf. This kind of change is one part of the organism s life cycle. A life cycle is the combination of birth, growth, life, and death. Changes in individuals can be drastic, such as the complete changing of body form called metamorphosis. Metamorphosis occurs in butterflies and frogs, for example. Other changes are subtle, such as a ruby-throated hummingbird increasing its fat reserves for migration. Change also takes place at the genetic level of individuals and their offspring. One type of genetic change is the process of mutation. A mutation is a change in the make up, or arrangement, of the genetic instructions for an organism. Sometimes mutations help an individual to survive better in its environment. Other mutations make it more difficult for an organism to survive. And still others are simply neutral and do not affect survival one way or another. When an animal reproduces, another kind of genetic change takes place. This change occurs during meiosis, a type of cell division that occurs in sex cells. Parental genes, or traits, on the cells are halved when new sex cells are made. When a male and female reproduce, the halved male and female sex cells come together to form the offspring. That offspring displays a combination of physical traits from both parents. For example, you might have your mother s eye color and your father s curly hair. But, the combination of all the traits is different from either parent. Some traits may have been hidden in the parents genetic makeup, but because of the shuffling, those traits may show up in the offspring. In this way, change has occurred at the genetic level from one generation (the parents) to the next (the offspring). Since organisms must reproduce in order for life to continue, survival and successful reproduction are paramount. If a mutation or trait helps an organism survive, the organism is more likely to reproduce and pass its genetic information to its offspring. If a mutation or trait is detrimental, the organism is less likely to survive and reproduce. Without reproduction and birth, the individual s genetic information will not be passed on. The more beneficial a trait is for survival and reproduction, the more likely that New Mexico Museum of Natural History & Science Proyecto Futuro 15

23 Introduction Life Science trait will persist in future generations. In other words, those traits are selected in the population. This process is called natural selection and results in biological adaptation. If an organism faces changes in its environment and a particular trait is selected, then the organism is said to have adapted to the environment. Biological adaptation occurs at the genetic level and requires at least one reproductive cycle. Over time, groups of organisms evolve because of natural selection and adaptation. It is sometimes difficult to convey to students that natural selection and biological adaptation are not deliberate acts. However, teachers must be very careful to describe the evolutionary process accurately. Organisms do not want to adapt or decide to select certain genetic traits. Likewise, the environment does not create traits or characteristics at the genetic level. The environment is only the testing ground for the existing genetic characteristics of an individual. Classification in the Life Sciences Biologists have looked to the past to understand how today s organisms live and interact with each other and their environment. Biologists map these associations by first studying the similarities among modern organisms and fossils. By determining the age of the rocks where fossils are found, scientists have learned when in Earth s history different organisms lived. Fossil records show the order in which animals developed over millions of years. This information is represented in a historical time line of organisms, called a geologic time line (Table 1). Biologists use this information to study how modern organisms are related to one another and to help them organize and classify groups of organisms. Now, imagine keeping track of 8,000 different kinds of birds or over 20,000 kinds of insects! What about classifying 1.4 million different types of living organisms? In order for biologists to make sense of all the different kinds of organisms, they group them with other similar organisms. In this way, biological information is organized much like a supermarket organizes its produce or a library organizes books. Scientific classification categorizes organisms into groups of similar organisms, but it also takes into account how those organisms are related to one another. Biologists who specialize in classification are called taxonomists. Taxonomists group organisms into large, general categories called kingdoms. The kingdom concept is similar to categorizing library books into fiction and non-fiction. 16 New Mexico Museum of Natural History & Science Proyecto Futuro

24 Introduction Life Science Table 1 Geologic Time Line ERA PERIOD MILLIONS OF YEARS AGO (APPROX.) MAJOR EVOLUTIONARY EVENTS Cenozoic Quaternary 0 to 1.8 Humans evolve Tertiary 1.8 to 65 Mammals and birds dominant Mesozoic Cretaceous 65 to 144 First placental mammals Flowering plants dominant Jurassic 144 to 200 First birds First flowering plants Triassic 200 to 251 First mammals First dinosaurs Paleozoic Permian 251 to 295 Cone-bearing plants dominant Carboniferous 295 to 355 First reptiles First seed plants Devonian 355 to 410 First amphibians First seeds (plants) Silurian 410 to 435 First fossil plants First jawed fish Ordovician 435 to 500 Algae dominant First fungi Cambrian 500 to 540 First vertebrates Simple invertebrates Precambrian Precambrian Before 540 Life diversifies Eukaryotes Prokaryotes Origin of Life New Mexico Museum of Natural History & Science Proyecto Futuro 17

25 Introduction Life Science Table 2 Characteristics of the Four Kingdoms of Eukaryota KINGDOM MAJOR MODE OF FEEDING MOTILITY (MOVEMENT) Protista Absorb, ingest, or Both motile and non-motile photosynthesize Fungi Absorb Generally non-motile Plantae Photosynthesize Generally non-motile Animalia Ingest All motile at some stage There are currently four recognized kingdoms: protists (Protista), fungi (Fungi), plants (Plantae), and animals (Animalia) (Table 2). Older texts often include a fifth kingdom, the Monera, which includes bacteria. However, as biologists learned more about bacteria, they discovered they were very different from all other organisms so different, that bacteria are now included in a new category called a domain. The three domains are the Bacteria domain; the Eukaryota domain, which includes four kingdoms (protists, fungi, plants, and animals); and a new domain, called Archaea, which includes bacteria-like organisms with a genetic makeup that is very different from bacteria. Just as the fiction category in the library includes mysteries, westerns, and romantic novels, kingdoms also include other categories of organisms. Beneath the kingdom, the categories are arranged in descending order or in a hierarchy (Table 3). This means that the categories at each level contain all the organisms in the categories below. The top of the hierarchy contains larger groups of organisms that are similar, but not necessarily closely related. For example, humans, porcupines, and black bears are all mammals, but are only distantly related. They share the same categories at the top levels: kingdom Animalia, phylum Chordata and class Mammalia. But, humans belong to the Order Primates, porcupines belong to the Order Rodentia, and black bears belong to the Order Carnivora. The increasingly smaller categories contain organisms that are more similar and more closely related. For example, wolves, bears, and cougars are all meat eaters and belong to the order Carnivora. Even more closely related are dogs, wolves, and coyotes, 18 New Mexico Museum of Natural History & Science Proyecto Futuro

26 Introduction Life Science Table 3 Hierarchy of Categories SAMPLE ANIMALS Bald Eagle Humans Porcupine Black Bears Crocodile Domestic (American) Dogs KINGDOM Animalia Animalia Animalia Animalia Animalia Animalia PHYLUM Chordata Chordata Chordata Chordata Chordata Chordata CLASS Aves Mammalia Mammalia Mammalia Reptilia Mammalia ORDER Falconiformes Primates Rodentia Carnivora Crocodylia Carnivora FAMILY Accipitridae Hominidae Erethizontidae Ursidae Crocodylidae Canidae GENUS Haliaeetus Homo Erethizon Ursus Crocodylus Canis SPECIES leucocephalus sapiens dorsatum americanus acutus familiaris which all belong to the genus Canis. This system of scientific classification helps biologists organize the vast quantity of organisms that have been identified. It also makes the huge job of sorting through and classifying the vast array of newly discovered organisms much easier! Naming Species When identifying each individual species, scientists use a naming system developed by Carolus Linnaeus in the 1700 s. Binomial nomenclature is a system that uses two Latin names to identify the genus and species of each organism. These scientific names are used worldwide by scientists and they help eliminate the confusion sometimes caused when a species has multiple common names in several different languages. An organism s scientific name is always italicized or underlined. The genus name always begins with a capital letter, but the species name is always lower case. For example, the scientific name for humans is written: Homo sapiens or Homo sapiens. Homo is the New Mexico Museum of Natural History & Science Proyecto Futuro 19

27 Introduction Life Science name of the genus, and sapiens is the name of the species. These basic rules, once learned, make the exchange of information between biologists clear and concise. References Appel, Gary. The Life Lab Science Program. Science and Children. National Science Teachers Association, Arlington, VA Beres, Samantha. 101 Things Every Kid Should Know About Science. Los Angeles, CA: RGA Publishing Group, Inc., Sylvia S. Mader, editor. Biology. 5 th Ed. Dubuque, IA: Wm. C. Brown Publishers, New Mexico State Department of Education. Content Standards with Benchmarks for Kindergarten Through 12 th Grade Science. School Program and Professional Development Unit Eisenberg, Evan. The Ecology of Eden. New York, NY: Vintage Books, Gega, P.C. and J.M. Peters, editors. How to Teach Elementary School Science. Upper Saddle River, NJ: Prentice-Hall, Inc., Kneidel, S. S. Creepy Crawlies and the Scientific Method: Over 100 Hands-On Science Experiments for Children. Golden, CO.: Fulcrum Publishing, National Academy of Sciences. National Science Education Standards: Life Science Available on National Science Teachers Association Home Page, Sagan, Dorion, and Lynn Margulis. Garden of Microbial Delights: A Practical Guide to the Subvisible World. Boston, MA: Harcourt Brace Jovanovich, Inc., New Mexico Museum of Natural History & Science Proyecto Futuro

28 Introduction Life Science INFORMACIÓN BÁSICA LAS CIENCIAS DE LA VIDA Características de los seres vivos Los seres vivos (bióticos) tienen varias características que los distinguen de los objetos no vivos (abióticos). Están compuestos por una o más células. Los seres vivos tienen estructuras que realizan funciones específicas. Los seres vivos tienen un medio interno. Este medio interno puede ser una sola célula o puede tratarse de un organismo multicelular. Los seres vivos necesitan y utilizan energía. Esta energía se usa para realizar funciones vitales. Las funciones vitales de los seres vivos abarcan, entre otras, la respiración, la excreción, el movimiento y el crecimiento. Los seres vivos se reproducen y pasan información genética a las generaciones futuras. Los seres vivos cambian o evolucionan a través del tiempo. Si un objeto no tiene todas estas características, no se lo considera un ser vivo. Por ejemplo, una bombilla de luz usa energía y tiene una estructura organizada pero no se mueve, ni respira ni se reproduce. Una esponja de mar no parece moverse, pero en realidad se mueve durante la primera etapa de su desarrollo y sólo en una etapa posterior se adhiere al fondo del mar o a algún otro objeto estacionario. Aunque todos los seres vivos tienen estas características en común, parece haber un número infinito de variaciones sobre el tema. De estas variaciones emana la enorme diversidad de tipos de vida que existen en la Tierra en la actualidad quizás entre 10 y 100 millones de especies diferentes. Hasta ahora, se han identificado 1.4 millones de especies. La célula La célula es la unidad estructural viviente más pequeña que existe, capaz de funcionar independientemente. De hecho, las células son tan pequeñas que podrías ubicar 9,000 de ellas, una al lado de la otra, en el espacio que ocupa un milímetro en una regla! Los naturalistas Robert Hooke y Anthony von Leeuvenhoek fueron los primeros en ver el mundo microscópico, a mediados de los años mil seiscientos. Hooke fue quien New Mexico Museum of Natural History & Science Proyecto Futuro 21

29 Introduction Life Science vacuola aparato de Golgi mitocondrios citoplasma retículo endoplasmático liso núcleo retículo endoplasmático áspero ribosoma (adherida al retículo endoplasmático) membrana celuósica lisosoma acuñó el término célula (del latín cellulla: celdilla) para describir las pequeñas celdas que vio en un corcho a través de su microscopio. Todos los seres vivos están compuestos de una o más células, pero no todas las células son iguales. Por ejemplo, las células de los protistas son muy diferentes de las células del sistema nervioso de los seres humanos y a la vez, muy diferentes de los glóbulos rojos. Sin embargo, existen similitudes entre todas las células. Estas características permiten a las células llevar a cabo sus funciones básicas 1) interactuar con el medio ambiente, 2) aprovechar energía, digerir y acumular alimentos. La membrana celular rodea a la célula por afuera. Es una capa delgada formada por sustancias químicas que actúan como guardián y puerta de entrada hacia el interior de la célula. La membrana es semipermeable y sólo permite que cierto tipo de químicos entren o salgan de la célula. El interior de la célula contiene citoplasma. El citoplasma es un fluido viscoso que actúa como si fuera la sangre de la célula, transporta alimentos y otras sustancias químicas de una parte de la célula a la otra. Otras partes de la célula también están ancladas al citoplasma. El núcleo y la mitocondria son dos de las estructuras que se encuentran en el citoplasma. La información genética (los genes están compuestos por ADN) está dentro del núcleo de la célula. Esta información genética determina qué tipo de célula será (nerviosa, sanguínea o protista) y cómo funcionará. La mitocondria es la planta de energía de la célula, donde los alimentos se transforman en la energía que usa la célula. 22 New Mexico Museum of Natural History & Science Proyecto Futuro

30 Introduction Life Science Otra estructura que se encuentra dentro del citoplasma son los lisosomas. Éstos contienen las enzimas que degradan los alimentos y eliminan los desechos producidos por las reacciones químicas dentro de la célula. Cuando los alimentos se digieren, los productos pasan a las vacuolas. Las vacuolas también son importantes para regular el agua dentro de la célula. Por ejemplo, las vacuolas de la planta la ayudan a que permanezca erguida y rígida. Cuando las vacuolas pierden mucha agua, la planta languidece. Cambios y adaptaciones Una de las características de los seres vivos es la organización y el orden, pero es el cambio lo que prevalece. El cambio ocurre a distintos niveles biológicos. Ocurre en organismos individuales, en grupos de seres vivos y en ecosistemas. Por ejemplo, un ser vivo cambia al crecer y madurar. Un lobo recién nacido tiene forma, tamaño y comportamiento diferentes de los de un lobo adulto. Este tipo de cambio es una de las partes del ciclo vital del organismo. El ciclo vital es una combinación de nacimiento, crecimiento, vida y muerte. Los cambios que sufren algunos individuos pueden parecer drásticos, por ejemplo la transformación total de la forma del cuerpo llamado metamorfosis. La metamorfosis ocurre en animales tales como las mariposas y las ranas. Hay otros cambios más sutiles, por ejemplo, el colibrí de pecho rojo que acumula reservas de grasa para utilizar durante el proceso migratorio. Las transformaciones a nivel genético también ocurren en los individuos y en su progenie. Un tipo de cambio genético proviene de las mutaciones. Una mutación es un cambio en la organización o configuración de la información genética de un organismo. A veces las mutaciones ayudan a que un individuo pueda sobrevivir más facilmente en su medio ambiente. Otras mutaciones dificultan la supervivencia del organismo. Y, otras mutaciones son simplemente neutrales y no afectan la supervivencia de manera alguna. Otro tipo de cambio genético ocurre con la reproducción de los animales. Este cambio se observa durante la meiosis, un cierto tipo de división celular que ocurre en las células sexuales. Los genes de los padres, es decir los rasgos que están impresos en las células se dividen por la mitad cuando se forman nuevas células sexuales. Cuando un macho y una hembra se reproducen, la mitad de las células sexuales masculinas y la mitad de las células femeninas se juntan para formar el nuevo ser. Ese nuevo ser tiene una combinación de características físicas de ambos padres. Por ejemplo, tú puedes tener el color de ojos de tu madre y el cabello rizado de tu padre. Pero, la New Mexico Museum of Natural History & Science Proyecto Futuro 23

31 Introduction Life Science combinación de todos estos rasgo será diferente a ambos padres. Algunos rasgos pudieron haber permanecido escondidos dentro de la estructura genética de los padres pero como se mezclan todos otra vez, es posible que resurjan en el nuevo ser. De esta manera, un cambio al nivel genético ocurre de generación (los padres) a generación (los hijos). Ya que la mayoría de estos seres vivos se reproducen para que la vida continúe, la supervivencia y la reproducción exitosa tienen suprema importancia. Si alguna mutación o algún rasgo ayuda a que el ser vivo sobreviva, este organismo tiene más posibilidades de reproducirse y de pasar este rasgo genético a su progenie. Si esta mutación o rasgo genético es perjudicial, entonces el organismo tendrá menos posibilidades de sobrevivir y reproducirse. Sin reproducción y nacimiento, la información genética del individuo no pasará a otras generaciones. Cuanto más beneficioso sea el rasgo para la supervivencia y la reproducción, tanto más probable es que ese rasgo persista y se transmita a futuras generaciones. En otras palabras, esas son las características seleccionadas para esa población. Este proceso se llama selección natural y el resultado es la adaptación biológica. Si un ser vivo se enfrenta con cambios en el medio ambiente y selecciona esa característica en particular, entonces se dice que ese ser vivo se ha adaptado al medio ambiente. La adaptación biológica ocurre al nivel genético y requiere que, por lo menos, se produzca un ciclo reproductivo. A través del tiempo, los grupos de seres vivos evolucionan debido a la selección natural y a la adaptación. A veces es fácil confundirse y pensar que la selección natural y la adaptación biológica son acciones deliberadas. Sin embargo, las maestras deben prestar atención y describir el proceso evolutivo con precisión. Los organismos ni desean ni deciden seleccionar determinados rasgos. De la misma manera, el medio ambiente no crea los rasgos o las características genéticas. El medio ambiente es sólo el lugar donde se prueban las características genéticas de cada individuo. Ciencias de la vida: clasificación Los biólogos estudian el pasado para entender cómo viven los organismos actuales y cómo interactúan entre ellos y con el medio ambiente. Los biólogos hacen mapas de estas asociaciones estudiando, primero, las similitudes entre organismos modernos y fósiles. Los científicos han aprendido en qué momento de la historia de la Tierra han habitado los diferentes organismos, fechando las rocas en donde se han encontrado dichos fósiles. La información recolectada sobre fósiles muestra el orden cronológico 24 New Mexico Museum of Natural History & Science Proyecto Futuro

32 Introduction Life Science Cuadro 1 Línea temporal geológica ERA PERÍODO HACE CUÁNTOS MILLIONES DE AÑOS (APROX.) PRINCIPALES ACONTECIMIENTOS EVOLUTIVOS Cenozoica Cuaternario Aparece el ser humano Terciario Los mamíferos y las aves dominan Mesozoica Cretácico Primeros mamíferos con placenta, las plantas con flores dominan la flora Jurásico Primeras aves Primeras plantas con flores Triásico Primeros mamíferos Primeros dinosaurios Paleozoica Pérmico Las plantas coníferas dominan la flora Carbonífero Primeros reptiles Primeras plantas de semillas Devónico Primeros anfibios Primeras semillas (plantas) Silúrico Primeras plantas fosilizadas Primeros peces mandibulados Ordovícico Dominan las algas Primeros hongos Cámbrico Primeros vertebrados Invertebrados simples Precámbrica Precámbrico Anterior a 540 La vida se diversifica Eucariotes Procariotes El orígen de la vida New Mexico Museum of Natural History & Science Proyecto Futuro 25

33 Introduction Life Science Cuadro 2 Características de los cuatro reinos de los eucariota REINO FORMA DE ALIMENTACÍON MOTILIDAD (MOVIMIENTO) Protista Absorción, ingestión o Tanto móvil como estacionario fotosíntesis Fungi Absorción Generalmente estacionario Plantae Fotosíntesis Generalmente estacionario Animalia Ingestión Todos móviles en alguna etapa en que los animales se desarrollaron a través de millones de años. Esta información se puede ver en la línea histórica temporal de los seres vivos, o línea geológica de tiempo (Cuadro 1). Los biólogos utilizan esta información para estudiar la relación de los seres vivos modernos entre ellos y para organizar y clasificar los organismos en grupos. Ahora, imagínate llevar la cuenta de 8,000 especies diferentes de aves o de 20,000 tipos de insectos! Y, piensa en clasificar 1.4 millones de seres vivos diferentes! Para que los biólogos puedan organizar y extraer información de todos los distintos tipos de organismos, los agrupan con otros seres vivos similares. De esta manera, la información biológica se organiza de manera parecida a la de los productos frescos en un supermercado o a la de los libros en una biblioteca. La clasificación científica ubica a los organismos en categorías con características similares, pero también toma en consideración la relación entre ellos. Los biólogos que se especializan en la clasificación de organismos se llaman taxónomos. Los taxónomos agrupan a los organismos en categorías generales y amplias llamadas reinos. El concepto de reinos tiene similitud con la categorización de libros en las bibliotecas: literatura novelística y no novelística (historia, biografías, ensayos, etc.). Actualmente existen cuatro reinos reconocidos: protistas (Protista), hongos (Fungi), plantas (Plantae) y animales (Animalia) (Cuadro 2). Los textos más antiguos hablan de un quinto reino que incluye las bacterias, el reino Monera. Sin embargo, a medida que 26 New Mexico Museum of Natural History & Science Proyecto Futuro

34 Introduction Life Science los biólogos descubrieron más sobre el tema, se dieron cuenta que las bacterias son muy diferentes de otros seres vivos tan diferentes, que en la actualidad las bacterias se incluyen en una categoría llamada dominio. Los tres dominios son el Bacteriano, el Eucariota que incluye los cuatro reinos (protista, hongos, plantas y animales) y un nuevo dominio llamado Archaea, que se creó cuando se descubrieron organismos del tipo de las bacterias pero con una composición genética muy diferente a la de las bacterias. De la misma manera que la categoría de novelas de la biblioteca incluye novelas policíacas, del lejano oeste y románticas, los reinos también incluyen categorías de seres vivos. Bajo el rótulo de reino, las categorías se organizan en orden de jerarquía descendente o ascendente (Cuadro 3). Esto significa que las categorías a cada nivel contienen todos los seres vivos de las categorías inferiores. El punto más alto de la jerarquía contiene grupos más amplios de seres vivos que son similares, pero no necesariamente relacionados. Por ejemplo, el ser humano, el puerco espín y el oso negro son todos mamíferos, pero no son parientes cercanos. Comparten las mismas categorías al nivel más alto de la jerarquía: reino Animalia, filo Chordata y clase Mammalia. Pero, el ser humano pertenece a la orden de los Primates, el puerco espín pertenece a la orden de los Rodentia y el oso negro pertenece a la orden de los Carnivora. Las categorías se hacen cada vez más pequeñas y a medida que se reducen contienen seres vivos cada vez más similares y más relacionados. Por ejemplo, tanto los lobos, como los osos y los pumas comen carne y pertenecen a la orden de los Carnívora. Pero los perros, los lobos y los coyotes tienen una relación más cercana; todos pertenecen al género Canis. Este sistema de clasificación científica ayuda a que los biólogos organicen la amplia variedad de seres vivos que han identificado. Además facilita el increíble trabajo de clasificar la gran gama de organismos que se siguen descubriendo! Los nombres de las especies Los científicos usan un sistema, inventado por Carolus Linnaeus en los años mil setecientos, que permite asignarle un nombre a cada una de las especies que identifican. La nomenclatura binomial es un sistema que utiliza dos nombres en latín para identificar el género y la especie de cada organismo. En el mundo de las ciencias se usan estos nombres científicos para evitar las confusiones que provienen de dar múltiples nombres comunes a cada especie en distintos idiomas. El nombre New Mexico Museum of Natural History & Science Proyecto Futuro 27